class Solution {
    public String[] reorderLogFiles(String[] logs) {
       int right = logs.length - 1;
		for (int index = right; index >= 0; index--) {
			String log = logs[index];
			if (isNumber(log.charAt(log.indexOf(" ") + 1))) {
				swap(logs, index, right);
				right--;
			}
		}
		sortWords(logs, 0, right);
        return logs;
    }
    private void sortWords(String[] logs, int start, int end) {
		if (start > end)
			return;
		int left = start;
		int right = end;
		int pivote = end;

		while (left < right) {
			while (left < right && compare(logs[left], logs[pivote]) < 0)
				left++;
			while (left < right && compare(logs[right], logs[pivote]) >= 0)
				right--;
			if (left < right) {
				swap(logs, left, right);
			}
		}
		swap(logs, right, pivote);
		sortWords(logs, start, right - 1);
		sortWords(logs, left + 1, end);

	}

	private int compare(String log1, String log2) {
		String str1 = log1.substring(log1.indexOf(" ") + 1);
		String str2 = log2.substring(log2.indexOf(" ") + 1);
		int val = str1.compareTo(str2);
		if (val == 0) {
			return log1.compareTo(log2);
		}
		return val;
	}

	private void swap(String[] logs, int index, int right) {
		String tmp = logs[index];
		logs[index] = logs[right];
		logs[right] = tmp;
	}

	private boolean isNumber(char charAt) {
		return charAt >= '0' && charAt <= '9';
	}
}